Kia and Hyundai released a software update on Monday after a viral TikTok challenge taught users how to hack the vehicles. But for now, it’s only available to a selected one million vehicles, out of the four million cars that will eventually need the patch.

It started as the “Kia Challenge” dating back to at least May on TikTok, demonstrating how “Kia Boys” use USB cords to hot-wire cars. Owners soon caught on to the widespread theft and began suing the car manufacturers for a lack of response. The class action lawsuit said that certain models of Kia and Hyundai cars lacked engine immobilizers, a common device that prevents car theft, making it easy to gain access, TechCrunch reported last September.

Car owners of affected models like the 2017-2020 Elantra, 2015-2019 Sonata and 2020-2021 Venue can visit a local dealership to install the anti-theft update, Hyundai said in a release. The updates include an anti-theft sticker to deter attack, a longer alarm, and the need for a physical key, rather than just a push start, to turn the vehicle on. Updates for other affected vehicles will be available by June, and you can find the whole list on Hyundai’s website.

In the meantime, Kia and Hyundai have provided about 26,000 steering wheel locks to vehicle owners to prevent theft, according to the National Highway Traffic Safety Administration. NHTSA got involved in the saga after thefts sparked by the Kia Challenge resulted in at least 14 reported crashes and eight fatalities, the agency said, turning it into a matter of public safety.